Tooth agenesis, the congenital absence of one or more permanent teeth, is the most common inherited disorder in humans, affecting up to 10% of the population, even when third molars are excluded. The condition occurs as an isolated anomaly or as part of dozens of syndromes and imposes significant functional, emotional and financial burdens on patients and their families. Since restoring esthetics and function for patients with tooth agenesis is complex and expensive, new therapies are warranted. Thus a central challenge relates to the critical need to translate the fruits of several decades of basic and clinical research on tooth development and tooth agenesis into tangible therapies that can benefit these patients. The long-range goals of this research are to develop replacement therapies that are safe and effective in correcting non-syndromic tooth agenesis in humans. We propose translational approaches that will test the hypotheses that the timely administration of select recombinant proteins or small molecule activators/inhibitors of major developmental signaling pathways will be able to replace missing or mutated gene products needed for tooth development. Furthermore, replacement proteins do not have to be identical with the tooth agenesis-causing protein as downstream targets/effectors of the mutated gene can also achieve the desired effect, either singly or in combination with other downstream effectors. Our approaches are inspired by the recent success in using recombinant Ectodysplasin A (rEDA) protein to treat X-linked hypohidrotic ectodermal dyslpasia (ED) in mice and dogs, results that led to clinical trials that are now assessing the safety and efficacy of rEDA therapy in humans with ED. Three aims are proposed as follows: (1) To explore the expanded use of EDA therapeutics for non-syndromic tooth agenesis. (2) To develop and evaluate novel Wnt therapeutics for non-syndromic tooth agenesis. (3) To identify new tooth agenesis genes through the use of human genetics approaches. The project addresses an important problem of high clinical relevance for which there are no cures. Data from these translational studies will provide the proof of principles needed to test whether such therapies can be used to restore tooth development in humans affected by non-syndromic tooth agenesis. In the broadest sense, this research will impact concepts and technologies that drive the field of therapies for other single gene disorders affecting the craniofacial complex and other systems.